CODEWITHSUNDEEP
scala
ovgolovin
ovgolovin

Reputation: 13420

Tuple unpacking inside map

I would like to unpack tuples inside map to access some of the values.

In Python I would do it this way:

>>> [topic for topic, partition in [('x', 1), ('y', 2)]]
['x', 'y']

Here tuples ('x', 1), ('y', 2) are unpacked into topic, partition, and then I access topic.

In Scala I have only managed to make it this way:

List(('x', 1), ('y', 2)).map(_._1)

But I would like to have explicit unpack into tuple as an itermediate step (even if it introduces some overhead) as I think it makes the code more readable.

I would like to achieve something like

List(('x', 1), ('y', 2)).map((topic, partition) => topic)

Unfortunatelly it didn't work:

> <console>:9: error: wrong number of parameters; expected = 1
                List(('x', 1), ('y', 2)).map((topic, partition) => topic)

Other attempts (e.g. List(('x', 1), ('y', 2)).map(Tuple2(topic, partition) => topic)) also failed.

Is there any way to achieve something similar to what I have in Python?

Upvotes: 2

Views: 273

Answers (1)

serejja
serejja

Reputation: 23881

Are you looking for this?

List(('x', 1), ('y', 2)).map {
  case (topic, partition) => topic
}

Edit: one more way to do the same, as @senia suggested:

for { 
  (topic, partition) <- List(('x', 1), ('y', 2)) 
} yield topic

Upvotes: 4

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